According to an arrangement known from French Pat. No. 2 321 417, the distributor, which can be a slide valve or turning valve, is sensitive to the application of a torque to the steering shaft to create a pressure difference between the two chambers of the jack and to produce a booster force which is transmitted to the rack to facilitate operation of the steering of the vehicle by the steering shaft and the driving pinion of the rack.
When no torque is applied to the steering shaft, the valve is in rest position and the pressure is the same in both chambers of the jack which corresponds to a booster force having a zero value.
According to an arrangement known from French Pat. No. 2 470 883, the distributor slide is also drawn toward its neutral position by the pressure prevailing in the two control chambers each of which is in communication with the line of a control pump, which can be adjusted by a manually operated unit, and by a nonreturn valve system, with a main pump.
To increase the response time of the jack, and arrangement of the distributor slide provides throttling passages which make a control chamber of the slide communicate with the supply line of the jack and with the line connecting the distributor to the tank.
Other types of power steering reduce the booster rate at high speeds or make the boost act only in a range of low speeds or during parking maneuvers. Steering known from French Pat. No. 2 434 744 receives a boost in a range of set speeds and uses an electronic control for processing signals produced by speed and torque sensors. The electronic control will advantageously have a computer and microprocess structure which will be able to perform multiple functions from a specific program.